All cases of cardiac infarction, acute coronary insufficiency and sudden death occurring in residents of the London Borough of Tower Hamlets below age 65 were registered over nearly three years, and survivors were followed up for one year. The attack-rate in men aged 45-64 years was 1 per 100 per annum but the recurrence-rate in survivors was 1 per 100 per month. Immigrants from Asia had more than the average, and those from the Carribean one tenth of the average attack-rate. Although it was unusual for general practitioners to manage cases at home by choice, nonetheless two-thirds of the deaths happened outside hospital and half of these were not witnessed. Half of those suffering coronary heart-attacks had a previous history of coronary disease and a sizable minority were already unfit for work. Approximately half of those attacked were alive at one year.